Parasitic and Reliability Issues of GaN-Based High Electron Mobility Transistors

In this tutorial recent reliability data under DC and RF operation and the current understanding of the major degradation mechanisms will be presented. In particular, failure modes and mechanisms of GaN HEMTs, identified within the framework of various accelerated tests, including step-stress short tests (< 150 hours) and life tests with a duration exceeding 3000 hours, will be presented. The proposed methodology includes a detailed characterization of the main parasitic effects in GaN HEMTs devices (gate leakage current, current collapse, kink effect, …) by means of DC and pulsed electrical measurements. The observed failure modes are subsequently analyzed by two-dimensional device simulations, in order to validate hypotheses on physical failure mechanisms. Electroluminescence microscopy and spectroscopy is adopted to evaluate hot carrier effects in GaN HEMTs, and as a powerful failure analysis tool.